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{ Statement

Begins a non-sectional, nestable loop.

The { and } statements can be used to repeat a group of score statements. These loops do not constitute independent score sections and thus may repeat events within the same section. Multiple loops may overlap in time or be nested within each other.

Syntax

{ p1 p2

Initialization

p1 -- Number of times to repeat the loop.

p2 -- A macro name that is automatically defined at the beginning of the loop and whose value is advanced with each repetition (optional). The initial value is zero and the final value is (p1 - 1).

Performance

The { statement is used in conjunction with the } statement to define repeating groups of other score events. A score loop begins with the { statement which defines the number of repetitions and a unique macro name that will contain the current loop counter. The body of a loop can contain any number of other events (including sectional breaks) and is terminated by a } statement on its own line. The } statement takes no parameters.

The use of the term "loop" here does not imply any sort of temporal succession to the loop iterations. In other words, the p2 values of the events inside of the loop are not automatically incremented by the length of the loop in each repetition. This is actually an advantage since it allows groups of simulataneous events to be easily defined as well. The loop macro can be used along with score expressions to increase the start times of events or to vary the events in any other way desired for each iteration. The macro is incremented by one for each repetition. Note that unlike the r statement, the value of the macro the first time through the loop is zero (0), not one (1). Therefore the final value is one less than the number of repetitions.

Score loops are a very powerful tool. While similar to the section repeat facility (the r statement), their chief advantage is that the score events in successive iterations of the loop are not separated by a section termination. Thus, it is possible to create multiple loops that overlap in time. Loops also can be nested within each other to a depth of 39 levels.

⚠ Warning

Because of serious problems of interaction with macro expansion, loops must start and end in the same file, and not in a macro.

Examples

Here are some examples of the { and } statements.

Sequentially repeat a three-note phrase four times.
{ 4 CNT

i1  [0.00 + 0.75 * $CNT.]   0.2   220
i1  [0.25 + 0.75 * $CNT.]   .     440
i1  [0.50 + 0.75 * $CNT.]   .     880

}

is interpreted as

i1  0.00   0.2   220
i1  0.25   .     440
i1  0.50   .     880

i1  0.75   0.2   220
i1  1.00   .     440
i1  1.25   .     880

i1  1.50   0.2   220
i1  1.75   .     440
i1  2.00   .     880

i1  2.25   0.2   220
i1  2.50   .     440
i1  2.75   .     880

In this example, p4 is assumed to be the frequency of the note event.

Create a group of simultaneous harmonic partials.
{ 8 PARTIAL
i1  0  1   [100 * ($PARTIAL. + 1)]
}

is interpreted as

i1  0  1   100
i1  0  1   200
i1  0  1   300
i1  0  1   400
i1  0  1   500
i1  0  1   600
i1  0  1   700
i1  0  1   800

Here is a full example of the { and } statements. It uses the file leftbrace.csd.

An example of nested loops to create several inharmonic sine clusters.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
; Audio out   Audio in
-odac           -iadc    ;;;RT audio I/O
; For Non-realtime ouput leave only the line below:
; -o abs.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>
nchnls = 2

gaReverbSend init 0

; a simple sine wave partial
instr 1
    idur   =       p3
    iamp   =       p4
    ifreq  =       p5
    aenv   linseg  0.0, 0.1*idur, iamp, 0.6*idur, iamp, 0.3*idur, 0.0
    aosc   oscili  aenv, ifreq, 1
           vincr   gaReverbSend, aosc
endin

; global reverb instrument
instr 2
    al, ar reverbsc gaReverbSend, gaReverbSend, 0.85, 12000
           outs     gaReverbSend+al, gaReverbSend+ar
           clear    gaReverbSend
endin

</CsInstruments>
<CsScore>
f1 0 4096 10 1

{ 4 CNT
  { 8 PARTIAL
      ;   start time     duration            amplitude          frequency

      i1  [0.5 * $CNT.]  [1 + ($CNT * 0.2)]  [500 + (~ * 200)]  [800 + (200 * $CNT.) + ($PARTIAL. * 20)]
  }
}

i2 0 6
e

</CsScore>
</CsoundSynthesizer>

See Also

Score Statements

Credits

Author: Gabriel Maldonado

New in Csound version 3.52 (?). (Fixed in version 5.08).